On 29 September, a tsunami triggered by a magnitude-8.3 earthquake hit Samoa, killing more than 100 people. Dale Dominey-Howes, of the Australian Tsunami Research Centre in Sydney, led a survey team commissioned by the United Nations Educational, Scientific and Cultural Organization's International Oceanographic Commission (UNESCO-IOC). He talks to Nature about what they saw.

Dale Dominey-Howes

Who was involved in the expedition to Samoa?

Our international survey team comprised more than 80 scientists from Samoa and from 16 institutions abroad. Field research on the two main islands of Samoa, Upolu and Savai'i, was undertaken between 14 and 21 October, and a post-event interim report was presented to the government of Samoa on 26 October.

What was the purpose of the survey?

This is the first time a post-tsunami survey has been undertaken in Samoa because it's the first time such an event has affected the country in modern times.

The main purpose was to explore the nature of the tsunami and its impacts in order to help the national government enhance its tsunami disaster risk management strategies. For the first time ever in a UNESCO-IOC assessment, we have attempted to explore the nature and linkages — if any — between the physical, social, economic and environmental systems to provide a more sophisticated understanding of the tsunami and its impacts — one that goes beyond a simple description of 'maximum run-up' or 'total number of lives lost'.

What did you find?

We recorded substantial inundation from the coast and surprisingly high maximum run-up of a little less than 15 metres above normal mean sea level. Flow depths of the tsunami (the depth of water flowing over the land surface) in some locations were extremely high. The tsunami had widespread impacts on the natural environment including erosion and deposition of sediments. Many coastal plants and trees were destroyed. Worse, damage to agricultural gardens has affected food supply for many families.

We have been able to identify the factors that influenced extensive damage to buildings. We have also spoken with local people who are experiencing severe trauma. Fear is a strong element of how people are feeling.

Was there anything particularly unusual about this tsunami?

In spite of historical accounts of 40 or so tsunamis since 1837, there is no social or cultural memory of tsunamis in Samoa. We find this very puzzling. It presents huge challenges to the disaster management office in convincing the people of Samoa that tsunamis are a real threat to coastal communities. A tsunami in 1917 seems to have been as large and probably as destructive as the 2009 event. But there is a clear need for undertaking palaeo-tsunami studies in the region, to address the issues of frequency and magnitude.

Tsunami survey team members work with community in heavily impacted coastal communities of Samoa. Credit: UNESCO-IOC ITST Samoa Team

How is awareness in the region?

The Samoan Disaster Management Office has worked hard in recent years to partner with communities to raise awareness of tsunamis and to develop — and practise — evacuation procedures. These efforts have saved many lives. Many Samoans reacted appropriately when the earthquake occurred: they moved inland without waiting for an official warning. Sadly, however, more than 100 people did lose their lives. This reminds us that scientists and governments alike must continue to work to improve disaster risk reduction efforts.

Could a more effective warning system have saved more lives?

In my opinion, no. The detection, monitoring and warning systems worked well and could not have done anything different. The earthquake that caused the tsunami occurred so close to the coast of Samoa that there was simply not enough time to process the seismic data and issue a warning (although the government did issue a warning as soon as it had clear information about a tsunami event). The take-home message is: if you feel an earthquake in the coastal zone, run to higher ground.

Are the survey results useful for improving preparedness?

Absolutely. We have been able to offer suggestions for improved building design and ecosystem management to reduce the damage of any future tsunami. Further, the socially oriented research undertaken has pointed to where, and how, enhanced disaster risk reduction activities should be focused. We have made many suggestions; it is now up to the Samoan authorities to decide how to use the information.